Every year, a variety of trees change their leaves to gold, crimson, amber, and even jewel-toned purple. For those who live in places without a major color shift, or on treeless plains, deserts, or deserted islands, feel free to scroll on by. Just kidding. Come back! Well, fine then. Today, we tackle an age-old question: Why are you wearing that sweater? Apologies. That’s apparently next week. Today’s question is: Why do some leaves fall off? Because they’ve had enough of the tree’s drama. We said it. Months of photosynthesis. Chlorophyll everywhere. Constant demands for sunlight. Not one person asking how the leaf is doing. Eventually, every leaf reaches its limit. Sorry. The supervisor is requesting a sidebar. And we’re back. Deciduous trees are responsible for much of the colorful annual display we associate with autumn. For most of the year, a green pigment called chlorophyll helps leaves capture sunlight for photosynthesis. But as days get shorter and tempe...